Approval Voting Breaks Duverger’s Law: Gives Voters More Options

Meet Maurice Duverger

Start telling people that a third party’s day is on its way and it’s only a matter of time before you hear about Duverger’s Law. But laws, like rules, are meant to be broken. And Duverger’s is no exception.

Academic and lawyer Maurice Duverger was in his mid-30s when he published Les Partis Politiques (Political Parties) in 1951. In his book, Maurice described how Plurality Voting leads to a two-party system. Plurality is the method where you choose only one candidate and the candidate with the most votes wins. In contrast, he proposed that proportional methods and, to a lesser extent, runoffs lead toward multi-party systems. Duverger’s insight into two-party systems became known as Duverger’s Law.

Spelling Out Duverger’s Law

Despite the word “law” Duverger was describing more of a tendency than an absolute certainty. He clearly appreciated the voting method’s dominant role in perpetuating or eliminating a two-party system. But he still recognized other factors.

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These factors included issues like ballot access, access to information, and third party desirability. Other scholars have offered their own factors. One example includes the number of dimensions within political issues facing the electorate. Are there three or more strongly supported positions within a big issue? If so, that could favor having more parties.

To get an idea of how Duverger’s Law behaves, it’s a good idea to understand the rationale behind its operation. Duverger said that Plurality tends toward a two-party system because of two factors:

1. High Threshold for Winners

Plurality, like all single-winner methods, demands a high threshold for election (more votes than anyone else). This makes victory difficult for parties with less support.

2. Wasted Votes

Plurality Voting causes voters to fear wasting their vote on candidates less likely to win. Consequently, voters are more likely to choose exclusively amongst the frontrunners. Voters appreciate that choosing amongst the frontrunners makes them more likely to determine the election’s winner.

Testing the Limits of Duverger’s Law

Let’s briefly hit the first factor: Single-winner methods require candidates to have a high threshold of support in order to win. All single-winner methods require this high threshold. Perhaps some methods’ vulnerability to vote splitting between similar candidates allows a third-party candidate to slip in from time-to-time. However, the high threshold largely keeps these alternatives out.

While Duverger’s first factor confronts all single-winner methods, the second does not. Not all single-winner methods cause voters to fear wasting their vote. One method in particular, Approval Voting, allows a voter to choose their favorite(s) without fear of repercussions. Always.

Approval Voting is simple: Just pick as many candidates as you like. There’s no ranking or anything complicated. Then the candidate with the most votes wins. Approval Voting is identical to Plurality except that when you choose more than one candidate, your ballot is still valid. Plurality, on the other hand, throws your ballot away.

So how does Approval Voting avoid the wasted vote syndrome? Under Approval Voting, even if you decide to vote for the “lesser of two evils,” you’re not required to stop. Remember, you can pick as many candidates as you want. So you can continue by choosing any other candidates you really support—regardless of viability.

Duverger’s Bumpy Road

Imagine a local election. The hot-button issue in your town is potholes. Big ones. You’ve sent your car in for realignment twice in the last month. Flats are worse. You’ve gotten one in each of the past three weeks. You feel like you’re in a Mars rover every time you start your car. It’s an abomination.

You scope out the candidates. Two are frontrunners from the major parties, and one is an independent. Among the frontrunners, one refuses to spend any money fixing potholes. Interestingly, the streets in this candidate’s part of town are uncannily smooth. This means there are actually voters that side with him. You hate this guy. You curse his name on your bumpy trips across town.

The other frontrunner is a bit wishy-washy on the issue. He says he’ll send out a crew with some cheap filler. But, he’ll only do this once every three months. An outside expert determines this will halve the number of pothole-related incidents. You can’t deny that needing alignments “a mere” once a month is an improvement. The same goes for reducing flats. But you’d prefer a better solution.

The independent, who happens to be a civil engineer, takes a different approach. She prefers to be proactive about road maintenance and she likes higher quality filler. She further vows a 48-hour turnaround on fixing new potholes. This would virtually eliminate the menace. A tax would be involved, but an outside expert finds that average savings on car repairs would more than compensate. You adore this woman. Still, you suspect her third-party status will cause your neighbors to see her as not viable. Admittedly, you suspect it yourself.

If this were Plurality Voting, then you’d likely be stuck picking the frontrunner proposing cheap filler. If you voted for the independent (great as she may be), then you could easily allow your hated frontrunner to win. And what a nightmare that would be! Further, the independent may not even get invited to debates because of her poor showing with Plurality polling. And those same polls can keep her from getting media access. Duverger’s second factor, fearing the wasted vote, is in full force.

Approval Voting’s Houdini Act

But what if this was an Approval Voting election? In that case, you would look at who was likely to win: one of the two frontrunners. If the frontrunner you hate is still competitive, then you’ll need to vote against him. You hedge your bets by voting for the other frontrunner, the one proposing cheap filler, but Approval Voting lets you keep going. Naturally, you also vote for the independent (your favorite) because of her comprehensive pothole plan.

An Approval Voting election is going to change the dynamics right away, all because it lets voters fearlessly choose their honest favorite. This lets alternatives not initially leading the pack to get a more accurate reflection of support. Thankfully, that more accurate reflection means our independent candidate’s appeal will actually get measured.

Escape from Duverger’s Law

Approval Voting lets voters choose their honest favorites without fearing a wasted vote. And so it escapes Duverger’s second factor. This more honest voting permits third party and independent candidates to build support. Using Approval Voting in surveys/polls will give alternative candidates easier debate access and media exposure.

With the absence of the wasted vote dilemma and the inclusion of good ideas, these candidates can even win. That’s good news for the independent in our pothole election. Smoother roads lie ahead.

So the next time someone brings up Duverger’s Law to bemoan the two-party system’s inevitability, you now have an answer. Tell them that Approval Voting completely bypasses Duverger’s second factor because voters can finally pick their honest favorite(s). A favorite candidate’s merit, not viability, is all that matters in Approval Voting — just as it should be. And not even Duverger’s Law can stand in the way.

About the Author

Aaron Hamlin

Aaron is the executive director of The Center for Election Science, a nonpartisan nonprofit that studies and promotes better electoral systems. He received his J.D. from Thomas M. Cooley Law School and has graduate degrees from Indiana University and Miami University in public health and educational psychology, respectively. He received his B.S. in psychology with mathematics minor from Northern Kentucky University.
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